This invention relates generally to computer aided design of structures fabricated from a number of plies, the structures possibly including one or more of inserts, cores, and subsystems, and more specifically, to methods and systems for explicit representation of such composite structures.
Heretofore, the descriptions resulting from computer aided design (CAD) of composite structures have been limited to implicit ply representations. These implicit methods make it extremely difficult to visualize and/or interrogate the resulting definitions for design intent information, for example, piercing, stacking, material, ply thickness, ply volume, ply orientation, and a overall thickness without specialized software. The above is especially true when model based definition is used, as opposed to a more conventional drawing based approach. While progress has been made in the definition of solids parts, there has been virtually no movement in the area of composite definitions. Prior approaches have been limited by the potential file size issues and the relational complexity of composite parts, which are fabricated from multiple layers, or plies, and which may include one or more of inserts, cores, and subsystems that, together with the plies, form one or more essentially inseparable assemblies.
For example, in one model based definition method each ply of a structure is represented as a surface. While this representation format provides a major improvement over two dimensional drawings and three dimensional wireframe representations, it still leaves ply thickness and stacking information as implied information. Plies represented as solids or shell solids would have explicit thicknesses, but unless they are generated and stacked properly, special programming is still required to derive the complete description of design intent.